Oh nasty, you poor thing!! I hate to say it, but I had the same pains from roughly 20 weeks right up until my waters broke. It's quite common and nothing really to worry about except that it's painful and quite debilitating. I used to crawl to the toilet in the middle of the night as my pelvis just couldn't support me until I'd 'warmed up' a bit. The deep groin pain was constant too and hurt most when I slept and rolling over was hell. That pain was caused by a muscle that's attached to the uterus so as it grows, the pain increases.

I saw physios who specialise in pregnancy/women's health the whole way through. I wore a belly brace a lot of the time too. Bring it up with your midwife but I'd also recommend going to see a good physio - but it's best that they are pregnancy specialists.

As one of the other girls mentioned, it could well be SPD but as you can stand on one leg, it sounds more like what I had which ended up being the muscle pulling in the groin and just dodgy hips & pelvis which didn't cope well with all the growing.

Big hugs, I know what you're going through